Biomass Char Compositions for Catalytic Gasification

ABSTRACT

Particulate compositions are described comprising an intimate mixture of a biomass char producedfrom the combustion of a biomass, such as switchgrass or hybrid poplar, with at least a second carbonaceous material, such as petroleum coke or coal, and, optionally a gasification catalyst, for gasification in the presence of steam to yield a plurality of gases including methane and at least one or more of hydrogen, carbon monoxide, and other higher hydrocarbons are formed. Processes are also provided for the preparation of the particulate compositions and converting the particulate composition into a plurality of gaseous products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 from U.S.Provisional Application Ser. No. 61/032,734 (filed Feb. 29, 2008), thedisclosure of which is incorporated by reference herein for all purposesas if fully set forth.

FIELD OF THE INVENTION

The present disclosure relates to particulate compositions comprisingbiomass gasification or combustion char and at least a secondcarbonaceous component as well as at least one gasification catalyst,where the char provides at least a portion of a gasification catalyst inthe composition. Further, the disclosure relates to processes forpreparation of the particulate compositions and for gasification of thesame in the presence of steam to form gaseous products, and inparticular, methane.

BACKGROUND OF THE INVENTION

In view of numerous factors such as higher energy prices andenvironmental concerns, the production of value-added gaseous productsfrom lower-fuel-value carbonaceous feedstocks, such as biomass, coal andpetroleum coke, is receiving renewed attention. The catalyticgasification of such materials to produce methane and other value-addedgases is disclosed, for example, in U.S. Pat. No. 3,828,474, U.S. Pat.No. 3,998,607, U.S. Pat. No. 4,057,512, U.S. Pat. No. 4,092,125, U.S.Pat. No. 4,094,650, U.S. Pat. No. 4,204,843, U.S. Pat. No. 4,468,231,U.S. Pat. No. 4,500,323, U.S. Pat. No. 4,541,841, U.S. Pat. No.4,551,155, U.S. Pat. No. 4558027, U.S. Pat. No. 4,606,105, U.S. Pat. No.4,617,027, U.S. Pat. No. 4,609,456, U.S. 5,017,282, U.S. Pat. No.5,055,181, U.S. Pat. No. 6,187,465, U.S. Pat. No. 6,790,430, U.S. Pat.No. 6,894,183, U.S. Pat. No. 6,955,695, US2003/0167961A1,US2006/0265953A1, US2007/000177A1, US2007/083072A1, US2007/0277437A1 andGB1599932.

An efficient process for the catalytic gasification of a carbonaceousmaterial to synthetic natural gas generally requires the presence of acatalyst to encourage the formation of methane with respect to otherproducts, such as syngas. It has generally been contemplated to providesuch a catalyst from a source external to the gasification process, forexample, by providing solutions or solid compositions of a catalystwhich are acquired separately from the feedstocks, adding additionalcosts to the process. However, as certain types of feedstock can containintrinsic catalytic compounds, there exists a need in the art to developprocesses for the catalytic gasification of carbonaceous materials whichtake advantage of such intrinsic catalysts to enable lower cost per unitenergy stored by increasing the utilization and conversion of thefeedstocks in the process.

SUMMARY OF THE INVENTION

The present disclosure relates to particulate compositions comprising abiomass char, a biomass and/or a non-biomass, and a gasificationcatalyst. Further, the disclosure relates to processes for preparationof the particulate compositions and for gasification of the same in thepresence of steam to form gaseous products, and in particular, methane.Through blending appropriate levels of biomass and/or non-biomassmaterials with the biomass char in the feedstock, more efficientutilization of the carbon in the biomass can be realized as well astaking advantage of intrinsic levels of alkali metal compounds presentin particular types of biomass char.

In a first aspect, the present invention provides a particulatecomposition having a particle distribution size suitable forgasification in a fluidized bed zone, the particulate compositioncomprising an intimate mixture of: (a) a first carbonaceous feedstockthat is a biomass char; (b) a second carbonaceous feedstock that is abiomass, non-biomass, or mixture thereof, and (c) a gasificationcatalyst which, in the presence of steam and under suitable temperatureand pressure, exhibits gasification activity whereby a plurality ofgases including methane and at least one or more of hydrogen, carbonmonoxide, carbon dioxide, hydrogen sulfide, ammonia and other higherhydrocarbons are formed, wherein (i) the first carbonaceous feedstockand second carbonaceous feedstock are present in the particulatecomposition at a weight ratio of from about 5:95 to about 95:5; (ii) thegasification catalyst comprises a source of at least one alkali metaland is present in an amount sufficient to provide, in the particulatecomposition, a ratio of alkali metal atoms of the gasification catalystto carbon atoms ranging from about 0.01 to about 0.10, wherein thebiomass char comprises at least a portion of the source of at least onealkali metal.

In a second aspect, the present invention provides a process forconverting a particulate composition into a plurality of gaseousproducts, the process comprising the steps of: (a) supplying aparticulate composition according to the first aspect to a gasifyingreactor; (b) reacting the particulate composition in the gasifyingreactor in the presence of steam and under suitable temperature andpressure to form a plurality of gaseous products including methane andat least one or more of hydrogen, carbon monoxide, carbon dioxide,hydrogen sulfide, ammonia and other higher hydrocarbons; and (c) atleast partially separating the plurality of gaseous products to producea stream comprising a predominant amount of one of the gaseous products.

In a third aspect, the present invention provides a process forpreparing a particulate composition according to the first aspect, theprocess comprising the steps of: (a) providing a first particulatecarbonaceous feedstock that is a biomass char, a second particulatecarbonaceous feedstock that is a biomass, non-biomass, or mixturethereof, and, optionally, an alkali metal gasification catalyst which,in the presence of steam and under suitable temperature and pressure,exhibits gasification activity whereby a plurality of gases includingmethane and at least one or more of hydrogen, carbon monoxide, carbondioxide, hydrogen sulfide, ammonia and other higher hydrocarbons areformed from the particulate composition; (b) mixing the firstparticulate carbonaceous feedstock, the second particulate carbonaceousfeedstock and, optionally, the alkali metal gasification catalyst toform a mixture; and (c) optionally thermally treating the mixture undera flow of inert dry gas to form the particulate composition, wherein thegasification catalyst comprises a source of at least one alkali metaland is present in an amount sufficient to provide, in the particulatecomposition, a ratio of alkali metal atoms of the gasification catalystto carbon atoms ranging from about 0.01 to about 0.10, wherein thebiomass char comprises at least a portion of the source of at least onealkali metal.

DETAILED DESCRIPTION

The present disclosure relates to a particulate composition, methods forthe preparation of the particulate composition, and methods for thecatalytic gasification of the particulate composition. Generally, theparticulate composition includes a biomass char in various blends withone or more biomass and/or non-biomass carbonaceous materials, forexample, coals and/or petroleum coke.

The present invention can be practiced, for example, using any of thedevelopments to catalytic gasification technology disclosed in commonlyowned US2007/0000177A1, US2007/0083072A1 and US2007/0277437A1; and U.S.patent application Ser. No. 12/178,380 (filed 23 Jul. 2008), Ser. No.12/234,012 (filed 19 Sep. 2008) and Ser. No. 12/234,018 (filed 19 Sep.2008). All of the above are incorporated by reference herein for allpurposes as if fully set forth.

Moreover, the present invention can be practiced in conjunction with thesubject matter of the following U.S. patent applications, each of whichwas filed on Dec. 28, 2008: Ser. No. 12/342,554, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/342,565, entitled “PETROLEUM COKE COMPOSITIONS FOR CATALYTICGASIFICATION”; Ser. No. 12/342,578, entitled “COAL COMPOSITIONS FORCATALYTIC GASIFICATION”; Ser. No. 12/342,596, entitled “PROCESSES FORMAKING SYNTHESIS GAS AND SYNGAS-DERIVED PRODUCTS”; Ser. No. 12/342,608,entitled “PETROLEUM COKE COMPOSITIONS FOR CATALYTIC GASIFICATION”; Ser.No. 12/342,628, entitled “PROCESSES FOR MAKING SYNGAS-DERIVED PRODUCTS”;Ser. No. 12/342,663, entitled “CARBONACEOUS FUELS AND PROCESSES FORMAKING AND USING THEM”; Ser. No. 12/342,715, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/342,736, entitled “CATALYTIC GASIFICATION PROCESS WITH RECOVERY OFALKALI METAL FROM CHAR”; Ser. No. 12/343,143, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/343,149, entitled “STEAM GENERATING SLURRY GASIFIER FOR THE CATALYTICGASIFICATION OF A CARBONACEOUS FEEDSTOCK”; and Ser. No. 12/343,159,entitled “CONTINUOUS PROCESSES FOR CONVERTING CARBONACEOUS FEEDSTOCKINTO GASEOUS PRODUCTS”. All of the above are incorporated by referenceherein for all purposes as if fully set forth.

Further, the present invention can be practiced in conjunction with thesubject matter of the following U.S. patent applications, each of whichwas filed concurrently herewith: Ser. No. ______, entitled “PROCESSESFOR MAKING ABSORBENTS AND PROCESSES FOR REMOVING CONTAMINANTS FROMFLUIDS USING THEM” (attorney docket no. FN-0019 US NP1); Ser. No.______, entitled “STEAM GENERATION PROCESSES UTILIZING BIOMASSFEEDSTOCKS” (attorney docket no. FN-0020 US NP1); Ser. No. ______,entitled “REDUCED CARBON FOOTPRINT STEAM GENERATION PROCESSES” (attorneydocket no. FN-0021 US NP1); Ser. No. ______, entitled “PROCESS ANDAPPARATUS FOR THE SEPARATION OF METHANE FROM A GAS STREAM” (attorneydocket no. FN-0022 US NP 1); Ser. No. ______, entitled “SELECTIVEREMOVAL AND RECOVERY OF ACID GASES FROM GASIFICATION PRODUCTS” (attorneydocket no. FN-0023 US NP1); Ser. No. ______, entitled “COAL COMPOSITIONSFOR CATALYTIC GASIFICATION” (attorney docket no. FN-0024 US NP1); Ser.No. ______, entitled “COAL COMPOSITIONS FOR CATALYTIC GASIFICATION”(attorney docket no. FN-0025 US NP1); Ser. No. ______, entitled “CO-FEEDOF BIOMASS AS SOURCE OF MAKEUP CATALYSTS FOR CATALYTIC COALGASIFICATION” (attorney docket no. FN-0026 US NP1); Ser. No. ______,entitled “COMPACTOR-FEEDER” (attorney docket no. FN-0027 US NP1); Ser.No. ______, entitled “CARBONACEOUS FINES RECYCLE” (attorney docket no.FN-0028 US NP1); Ser. No. ______, entitled “CATALYTIC GASIFICATIONPARTICULATE COMPOSITIONS” (attorney docket no. FN-0030 US NP1); and Ser.No. ______, entitled “BIOMASS COMPOSITIONS FOR CATALYTIC GASIFICATION”(attorney docket no. FN-0031 US NP1). All of the above are incorporatedherein by reference for all purposes as if fully set forth.

All publications, patent applications, patents and other referencesmentioned herein, if not otherwise indicated, are explicitlyincorporated by reference herein in their entirety for all purposes asif fully set forth.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. In case of conflict, thepresent specification, including definitions, will control.

Except where expressly noted, trademarks are shown in upper case.

Although methods and materials similar or equivalent to those describedherein can be used in the practice or testing of the present disclosure,suitable methods and materials are described herein.

Unless stated otherwise, all percentages, parts, ratios, etc., are byweight.

When an amount, concentration, or other value or parameter is given as arange, or a list of upper and lower values, this is to be understood asspecifically disclosing all ranges formed from any pair of any upper andlower range limits, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the present disclosure be limited to thespecific values recited when defining a range.

When the term “about” is used in describing a value or an end-point of arange, the disclosure should be understood to include the specific valueor end-point referred to.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but can include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

The use of “a” or “an” to describe the various elements and componentsherein is merely for convenience and to give a general sense of thedisclosure. This description should be read to include one or at leastone and the singular also includes the plural unless it is obvious thatit is meant otherwise.

The term “predominant” as used herein, means that the referenced itemcomprises the highest population of a referenced component with respectto any additional components within the referenced item.

The materials, methods, and examples herein are illustrative only and,except as specifically stated, are not intended to be limiting.

Biomass

The term “biomass” as used herein refers to carbonaceous materialsderived from recently (for example, within the past 100 years) livingorganisms, including plant-based biomass, animal-based biomass, andcatalytic biomass. For clarification, biomass does not includefossil-based carbonaceous materials, such as coal.

The term “plant-based biomass” as used herein means materials derivedfrom green plants, crops, algae, and trees, such as, but not limited to,sweet sorghum, bagasse, sugarcane, bamboo, hybrid poplar, hybrid willow,albizia trees, eucalyptus, alfalfa, clover, oil palm, switch-grass,sudangrass, millet, jatropha, and miscanthus (e.g.,Miscanthus×giganteus). Biomass further include wastes from agriculturalcultivation, processing, and/or degradation such as corn cobs and husks,corn stover, straw, nut shells, vegetable oils, canola oil, rapeseedoil, biodiesels, tree bark, wood chips, sawdust, and yard wastes.

The term “animal-based biomass” as used herein means wastes generatedfrom animal cultivation and/or utilization. For example, biomassincludes, but is not limited to, wastes from livestock cultivation andprocessing such as animal manure, guano, poultry litter, animal fats,and municipal solid wastes (e.g., sewage).

The term “catalytic biomass” as used herein refers to biomass, asdefined herein, whose combustion produces an ash comprising of one or acombination of alkali metal compounds (e.g., K₂O and/or Na₂O) that canfunction as a gasification catalyst in the context of the presentinvention. The amount of such alkali metal compounds may, for example,be at least 5 wt % based on the weight of the ash. For example,catalytic biomass includes, but is not limited to, switchgrass, hybridpoplar, hybrid willow, sugarcane, bamboo, miscanthus, cotton stalks,flax, verge grass, alfalfa, sunflower, poultry litter, kenaf (hibiscuscannabinus), thistle, and almond shells and husks.

Non-Biomass

The term “non-biomass”, as used herein, means those carbonaceousmaterials which are not encompassed by the term “biomass” as definedherein. For example, non-biomass include, but is not limited to,anthracite, bituminous coal, sub-bituminous coal, lignite, petroleumcoke, or mixtures thereof.

(a) Petroleum Coke

The terms “petroleum coke” and “petcoke” as used herein includes both(i) the solid thermal decomposition product of high-boiling hydrocarbonfractions obtained in petroleum processing (heavy residues—“residpetcoke”); and (ii) the solid thermal decomposition product ofprocessing tar sands (bituminous sands or oil sands—“tar sandspetcoke”). Such carbonization products include, for example, green,calcined, needle and fluidized bed petcoke.

Resid petcoke can also be derived from a crude oil, for example, bycoking processes used for upgrading heavy-gravity residual crude oil,which petoke contains ash as a minor component, typically about 1.0 wt %or less, and more typically about 0.5 wt % of less, based on the weightof the coke. Typically, the ash in such lower-ash cokes comprises metalssuch as nickel and vanadium.

Tar sands petcoke can be derived from an oil sand, for example, bycoking processes used for upgrading oil sand. Tar sands petcoke containsash as a minor component, typically in the range of about 2 wt % toabout 12 wt %, and more typically in the range of about 4 wt % to about12 wt %, based on the overall weight of the tar sands petcoke.Typically, the ash in such higher-ash cokes comprises materials such assilica and/or alumina.

Petroleum coke has an inherently low moisture content, typically, in therange of from about 0.2 to about 2 wt %. (based on total petroleum cokeweight); it also typically has a very low water soaking capacity toallow for conventional catalyst impregnation methods. The resultingparticulate compositions contain, for example, a lower average moisturecontent which increases the efficiency of downstream drying operationversus conventional drying operations.

The petroleum coke can comprise at least about 70 wt % carbon, at leastabout 80 wt % carbon, or at least about 90 wt % carbon, based on thetotal weight of the petroleum coke. Typically, the petroleum cokecomprises less than about 20 wt % percent inorganic compounds, based onthe weight of the petroleum coke.

(b) Coal

The term “coal” as used herein means peat, lignite, sub-bituminous coal,bituminous coal, anthracite, or mixtures thereof. In certainembodiments, the coal has a carbon content of less than about 85%, orless than about 80%, or less than about 75%, or less than about 70%, orless than about 65%, or less than about 60%, or less than about 55%, orless than about 50% by weight, based on the total coal weight. In otherembodiments, the coal has a carbon content ranging up to about 85%, orup to about 80%, or up to about 75% by weight, based on the total coalweight. Examples of useful coal include, but are not limited to,Illinois #6, Pittsburgh #8, Beulah (N. Dak.), Utah Blind Canyon, andPowder River Basin (PRB) coals. Anthracite, bituminous coal,sub-bituminous coal, and lignite coal may contain about 10 wt %, fromabout 5 to about 7 wt %, from about 4 to about 8 wt %, and from about 9to about 11 wt %, ash by total weight of the coal on a dry basis,respectively. However, the ash content of any particular coal sourcewill depend on the rank and source of the coal, as is familiar to thoseskilled in the art [see, for example, Coal Data: A Reference, EnergyInformation Administration, Office of Coal, Nuclear, Electric andAlternate Fuels, U.S. Department of Energy, DOE/EIA-0064(93), February1995].

The ash produced from a coal typically comprises both a fly ash and abottom ash, as are familiar to those skilled in the art. The fly ashfrom a bituminous coal can comprise from about 20 to about 60 wt %silica and from about 5 to about 35 wt % alumina, based on the totalweight of the fly ash. The fly ash from a sub-bituminous coal cancomprise from about 40 to about 60 wt % silica and from about 20 toabout 30 wt % alumina, based on the total weight of the fly ash. The flyash from a lignite coal can comprise from about 15 to about 45 wt %silica and from about 20 to about 25 wt % alumina, based on the totalweight of the fly ash [Meyers, et al. Fly Ash. A Highway ConstructionMaterial. Federal Highway Administration, Report No. FHWA-IP-76-16,Washington, D.C., 1976].

The bottom ash from a bituminous coal can comprise from about 40 toabout 60 wt % silica and from about 20 to about 30 wt % alumina, basedon the total weight of the bottom ash. The bottom ash from asub-bituminous coal can comprise from about 40 to about 50 wt % silicaand from about 15 to about 25 wt % alumina, based on the total weight ofthe bottom ash. The bottom ash from a lignite coal can comprise fromabout 30 to about 80 wt % silica and from about 10 to about 20 wt %alumina, based on the total weight of the bottom ash. [Moulton, Lyle K.“Bottom Ash and Boiler Slag,” Proceedings of the Third International AshUtilization Symposium. U.S. Bureau of Mines, Information Circular No.8640, Washington, D.C., 1973.]

Biomass Char

The term “biomass char” as used herein, means a char which is producedfrom the partial or complete gasification or combustion of a biomass.Such chars comprise an ash and can comprise residual carbon. The ash cancontain alkali metal compounds such as, but not limited to, sodium oxideand potassium oxide, and alkaline earth metal compounds such as, but notlimited to, calcium oxide, and mixtures thereof. One skilled in the artwill readily recognize that the residual carbon content of a biomasschar is dependent on the extent of combustion and/or gasification of abiomass as well as the composition of the biomass prior to gasificationand/or combustion. Further, one skilled in the art will readilyrecognize that the composition of the ash within a biomass char isdependent on the composition of a biomass, prior to gasification and/orcombustion and can be readily adjusted by, for example, blendingappropriate biomass feedstocks, as well as by the percent conversion ofcarbon in the biomass to gaseous products prior to withdrawal of thebiomass char from the relevant reactor.

A biomass char can be generated by providing a biomass particulate toany type of combustion and/or gasification reactor. Such reactors may beintegrated into a catalytic gasification process. For example, in anintegrated process, a biomass particulate can be provided to acombustion reactor in contact with a water source for the production ofsteam; such steam can be provided, in whole or in part, to a catalyticgasification reactor and the biomass char produced therein may beextracted and utilized for the preparation of a particulate compositionfor the catalytic gasification reactor. In various embodiments, aportion of the generated steam may be provided to a steam turbine forthe production of electricity. In other examples, a biomass char may beproduced from a biomass particulate to a gasification reactor for theproduction of a syngas. The syngas may be provided to a combustionturbine for the production of electricity.

In the preceding examples, the exhaust from the combustion reactor,gasification reactor, steam turbine, and/or combustion turbine producingthe biomass char may be exhausted to the atmosphere. Alternatively, inthe latter two embodiments, the exhaust from the steam turbine and/orcombustion turbine may be directed through a catalytic gasificationreactor wherein carbon dioxide in the exhausts may be recovered. Forexample, see previously incorporated U.S. patent applications Ser. No.______, entitled “STEAM GENERATION PROCESSES UTILIZING BIOMASSFEEDSTOCKS” (attorney docket no. FN-0020 US NP1), and Ser. No. ______,entitled “REDUCED CARBON FOOTPRINT STEAM GENERATION PROCESSES” (attorneydocket no. FN-0021 US NP1).

Preferably, the biomass char comprises an alkali metal source such thatthe biomass char provides at least a portion of the gasificationcatalyst in the particulate compositions described herein. In oneembodiment, the biomass char comprises substantially all, or all, of thegasification catalyst in the particulate compositions described herein.

While a biomass char can be produced from any of the biomass sourcesdiscussed above, as used throughout, the biomass char used in preparingthe particulate compositions herein is not required to be prepared fromthe same biomass as is utilized in preparing the particulatecompositions.

Particulate Compositions

The particulate compositions according to the present disclosure arebased on the above-described biomass char in combination with a biomassand/or a non-biomass, such as coal and/or petroleum coke, and agasification catalyst. Generally, the biomass char comprises an alkalimetal source such that the biomass char provides at least a portion ofthe gasification catalyst in the particulate composition. A furtherportion of the gasification catalyst can be optionally added tosupplement the biomass char. The further portion of gasificationcatalyst generally comprises an alkali metal source, typically, as analkali metal and/or an alkali metal compound.

Certain types of biomass, referred to herein as catalytic biomass,intrinsically contain significant levels of alkali metal compounds whichcan be found concentrated within a char produced from their gasificationand/or combustion. For example, catalytic biomass can be reacted in anytype of combustion or gasifying reactor to produce a biomass char havingincreased levels of alkali metal compounds (e.g., K₂O and/or Na₂O), withrespect to other biomass sources. Such biomass chars rich in such alkalimetal compounds can be extracted from a gasifier or combustion reactorand utilized for the preparation of the particulate compositions of thepresent invention. Examples of catalytic biomass include, but are notlimited to, switchgrass, hybrid poplar, hybrid willow, sugarcane,bamboo, miscanthus, cotton stalks, flax, verge grass, alfalfa,sunflower, poultry litter, kenaf (hibiscus cannabinus), thistle, andalmond shells and husks.

When an additional alkali metal source is present in the particulatecompositions, the alkali metal source may be loaded onto any of thebiomass char, the biomass, non-biomass particulates, as well as mixturesthereof. However, the alkali metal component may be blended into theparticulate composition as a separate particulate source.

The alkali metal source may be provided within the particulatecompositions to achieve an alkali metal content of from about 3 to about10 times more than the combined ash content of the particulatecomposition, on a mass basis. Typically, one or more alkali metalsources are present in an amount sufficient to provide, a ratio ofalkali metal atoms to carbon atoms in the particulate compositionranging from about 0.01, or from about 0.02, or from about 0.03, or fromabout 0.04, to about 0.10, or to about 0.08, or to about 0.07, or toabout 0.06.

Suitable alkali metals are lithium, sodium, potassium, rubidium, cesium,and mixtures thereof. Particularly useful are potassium sources.Suitable alkali metal compounds include alkali metal carbonates,bicarbonates, formates, oxalates, amides, hydroxides, acetates, orsimilar compounds. For example, the catalyst can comprise one or more ofsodium carbonate, potassium carbonate, rubidium carbonate, lithiumcarbonate, cesium carbonate, sodium hydroxide, potassium hydroxide,rubidium hydroxide or cesium hydroxide, and particularly, potassiumcarbonate and/or potassium hydroxide.

Co-catalysts or other catalyst additives may also be utilized, such asdisclosed in the previously incorporated references.

Each of biomass, biomass char, and non-biomass sources for theparticulate composition are typically supplied as a fine particulatehaving an average particle size of from about 25 microns, or from about45 microns, up to about 2500 microns, or up to about 500 microns. Oneskilled in the art can readily determine the appropriate particle sizefor the individual particulates and the particulate composition. Forexample, when a fluid bed gasification reactor is used, the particulatecomposition can have an average particle size which enables incipientfluidization of the particulate composition at the gas velocity used inthe fluid bed gasification reactor.

The ratio of the various particulates in each of the particulatecompositions can be selected based on technical considerations,processing economics, availability, and proximity of the non-biomass andbiomass sources. The availability and proximity of the sources for theparticulate compositions affect the price of the feeds, and thus, theoverall production costs of the catalytic gasification process. Forexample, the biomass char and non-biomass and/or biomass, can be blendedin at about 5:95, about 10:90, about 15:85, about 20:80, about 25:75,about 30:70, about 35:65, about 40:60, about 45:55, about 50:50, about55:45, about 60:40, about 65:35, about 70:20, about 75:25, about 80:20,about 85:15, about 90:10, or about 95:5 by weight on a wet or dry basis,depending on the processing conditions.

In one embodiment, at least the non-biomass particulate of theparticulate composition comprises the gasification catalyst. In anotherembodiment, the biomass particulate comprises the gasification catalyst.In another embodiment, both the biomass and non-biomass particulatescomprise a gasification catalyst. In yet another embodiment, the biomasschar comprises the gasification catalyst. In each of the precedingembodiments, an optional a co-catalyst/catalyst additive, as discussedpreviously, may be added to any one or more of the particulates.

The biomass and non-biomass sources, as well as the ratio of the biomassparticulate to the non-biomass particulate, can be used to control othermaterial characteristics of the feedstock blend.

Non-biomass materials, such as coals, typically include significantquantities of inorganic matter including calcium, alumina and silicawhich form inorganic oxides (i.e., ash) in the gasification reactor. Attemperatures above about 500° C. to about 600° C., potassium and otheralkali metals can react with the alumina and silica in ash to forminsoluble alkali aluminosilicates. In this form, the alkali metal issubstantially water-insoluble and inactive as a catalyst. To preventbuildup of the residue in the gasification reactor, a solid purge ofchar comprising ash, unreacted carbonaceous material, and various alkalimetal compounds (both water soluble and water insoluble) are routinelywithdrawn. Preferably, the alkali metal is recovered from the char, andany unrecovered catalyst is generally compensated by a catalyst make-upstream. The more alumina and silica that is in the feedstock, the morecostly it is to obtain a higher alkali metal recovery.

In preparing the particulate compositions of the present invention, theash content of the biomass, biomass char, and non-biomass particulatescan be selected to be, for example, to be about 20 wt % or less, orabout 15 wt % or less, or about 10 wt % or less, or about 5 wt % orless, depending on ratio of the particulates and/or the starting ash inthe non-biomass source. In other embodiments, the resulting particulatecomposition can comprise an ash content ranging from about 5 wt %, orfrom about 10 wt %, to about 20 wt %, or to about 15 wt %, based on theweight of the particulate composition. In other embodiments, the ashcontent of the particulate composition can comprise less than about 20wt %, or less than about 15 wt %, or less than about 10 wt %, or lessthan about 8 wt %, or less than about 6 wt % alumina, based on theweight of the ash. In certain embodiments, the resulting particulatecomposition can comprise an ash content of less than about 20 wt %,based on the weight of the particulate composition where the ash contentof the particulate composition comprises less than about 20 wt %alumina, or less than about 15 wt % alumina, based on the weight of theash.

Such lower alumina values in the particulate composition allow fordecreased losses of alkali catalysts in the gasification process.Typically, alumina can react with alkali source to yield an insolublechar comprising, for example, an alkali aluminate or aluminosilicate.Such insoluble char can lead to decreased catalyst recovery (i.e.,increased catalyst loss), and thus, require additional costs of make-upcatalyst in the overall gasification process, as will be discussedlater.

Additionally, the resulting particulate compositions can have asignificantly higher carbon content, and thus btu/lb value and methaneproduct per unit weight of the particulate composition. In certainembodiments, the resulting particulate composition has a carbon contentranging from about 75 wt %, or from about 80 wt %, or from about 85 wt%, or from about 90 wt %, up to about 95 wt %, based on the combinedweight of the non-biomass and biomass.

Through the recycling or reuse of a biomass char, whether from acatalytic biomass or any other type of biomass, increased carbonconversion efficiencies may be realized for the catalytic biomass.

Methods for Making the Particulate Composition

The biomass char, and biomass, and non-biomass sources typically requireinitial processing to prepare the particulate composition forgasification. Each component of the particulate composition may beseparately processed, for example, to crush the sources to prepareappropriately sized particulates and/or to add one or more gasificationcatalysts, and subsequently mixed.

The particulates can be prepared via crushing and/or grinding, eitherseparately or together, according to any methods known in the art, suchas impact crushing and wet or dry grinding to yield particulates.Depending on the method utilized for crushing and/or grinding, theresuiting particulates may be sized (i.e., separated according to size)to provide an appropriate feedstock.

Any method known to those skilled in the art can be used to size theparticulates. For example, sizing can be preformed by screening orpassing the particulates through a screen or number of screens.Screening equipment can include grizzlies, bar screens, and wire meshscreens. Screens can be static or incorporate mechanisms to shake orvibrate the screen. Alternatively, classification can be used toseparate the biomass char, biomass, and non-biomass particulates.Classification equipment can include ore sorters, gas cyclones,hydrocyclones, rake classifiers, rotating trommels, or fluidizedclassifiers. The biomass char, biomass, and non-biomass can be alsosized or classified prior to grinding and/or crushing.

Additional feedstock processing steps may be necessary. Biomass maycontain high moisture contents, such as green plants and grasses, canrequire drying prior to crushing; like-wise, non-biomass such ashigh-moisture coals, can require drying prior to crushing. Some cakingcoals can require partial oxidation to simplify gasification reactoroperation. Non-biomass feedstocks deficient in ion-exchange sites, suchas anthracites or low-sulfur petroleum cokes, can be pre-treated tocreate additional ion-exchange sites to facilitate catalysts loadingand/or association. Such pre-treatments can be accomplished by anymethod known to the art that creates ion-exchange capable sites and/orenhances the porosity of the feedstock (see, for example, previouslyincorporated U.S. Pat. No. 4,468,231 and GB1599932). Often,pre-treatment is accomplished in an oxidative manner using any oxidantknown to the art.

In one example, the non-biomass and/or biomass and/or biomass char iswet ground and sized (e.g., to a particle size distribution of 25 to2500 microns) and then drained of its free water (i.e., dewatered) to awet cake consistency. Examples of suitable methods for the wet grinding,sizing, and dewatering are known to those skilled in the art; forexample, see previously incorporated U.S. patent application Ser. No.12/178,380 (filed 23 Jul. 2008).

The particulate filter cakes formed by the wet grinding in accordancewith one embodiment of the present disclosure can have a moisturecontent ranging from about 40% to about 60%, about 40% to about 55%, orbelow 50%, based on the total weight of the cakes. It will beappreciated by one of ordinary skill in the art that the moisturecontent of dewatered wet ground biomass char and/or non-biomass and/orbiomass particulates depends on the particular type of non-biomass orbiomass, the particle size distribution, and the particular dewateringequipment used.

In certain embodiments, the biomass char comprises all of thegasification catalyst for preparing the particulate compositions of thepresent invention. In such cases, each of the particulates can be mixedas a wet cake or as a dry particulate, depending on the techniques usedfor preparation of each the particulates, to form a mixture (supra). Forexample, a dry particulate can prepared by thermally treating theparticulate wet cakes generated from wet grinding of a biomass char,biomass, and/or non-biomass. When the particulates are mixed as dryparticulates, then the mixture can be the particulate composition of theinvention. However, the mixture may be optionally thermally treated toprovide the particulate composition having, for example, a residualmoisture content of less than about 4 wt %. Optionally, a secondcatalytic component (e.g., a second gasification catalyst or aco-catalyst or other additive) can be provided to one or more of theparticulates; in such instances, the particulates can be treated inseparate processing steps to provide the second component, as discussedbelow.

Alternatively, when a portion of the gasification catalyst is suppliedby the biomass char, the biomass char and/or non-biomass and/or biomassparticulates can subsequently treated to associate the remaining portionof the gasification catalyst therewith. Optionally, a second catalyticcomponent (e.g., a second gasification catalyst or a co-catalyst orother additive) can be provided to one or more of the particulates; insuch instances, the particulates can be treated in separate processingsteps to provide the first catalyst and second component. For example,at least a portion of the primary gasification catalyst can be suppliedto a biomass char, non-biomass, and/or biomass particulate (e.g., apotassium and/or sodium source), followed by a separate treatment toprovide a calcium gasification co-catalyst source to the non-biomassand/or biomass particulate. Alternatively, at least a portion of thefirst catalyst and second component can be provided as a mixture in asingle treatment to a particulate; or a particulate (e.g., thenon-biomass) may be treated with a first catalyst and a secondparticulate (e.g., biomass) may be treated with a second component andthe two treated particulates blended. Any of the particulate wet cakesmay be mixed (e.g. by kneading) and the resulting mixture may be treatedwith a first and optionally, second catalyst (see, previouslyincorporated US2007/0000177A1).

In particular, the particulates may be treated with catalysts andblended according to any of the following permutations shown in Table 1,where A is a biomass char particulate comprising a portion of thegasification catalyst, B is a biomass particulate, and C is anon-biomass particulate; ‘*’ indicates that the particulate orparticulate mixture has been treated with part or all of the remainingportion of the catalyst (‘cat.’):

TABLE 1 Mixing particulates before catalyst treatment: A + B → AB A + C→ AC B + C → BC A + B + C → ABC AB + C → ABC BC + A → ABC Catalysttreatment: A + cat. → A* B + cat. → B* C + cat. → C* AB + cat. → (AB)*AC + cat. → (AC)* BC + cat. → (BC)* ABC + cat. -> (ABC)* Mixingparticulates after catalyst treatment: (a) One component treated withcatalyst A* + B → A*B A* + C → A*C A* + BC → A*BC A + B* → AB* AC + B* →(AC)B* A + C* → AC* AB + C* → (AB)C* (AB)* + C → (AB)*C (AC)* + B →(AC)*B (BC)* + A → A(BC)* (b) Two components treated with catalyst A* +B* → A*B* A* + C* → A*C* A* + (BC)* → A*(BC)* A* + B* + C → A*B*C A* +B + C* → A*BC* B* + (AC)* → B*(AC)* C* + (AB)* → (AB)*C* (c) Threecomponents treated with catalyst A* + B* + C* → A*B*C*

Any methods known to those skilled in the art can be used to associateone or more gasification catalysts with the biomass char, non-biomass,biomass particulates, and/or mixtures thereof to provide a catalyzedparticulate thereof. Such methods include but are not limited to,ad-mixing with a solid catalyst source and impregnating the catalyst onto particulates. Several impregnation methods known to those skilled inthe art can be employed to incorporate the gasification catalysts. Thesemethods include but are not limited to, incipient wetness impregnation,evaporative impregnation, vacuum impregnation, dip impregnation, ionexchanging, and combinations of these methods.

In one embodiment, an alkali metal gasification catalyst can beimpregnated into one or more of the particulates by slurrying with asolution (e.g., aqueous) of the catalyst. When a particulate is slurriedwith a solution of the catalyst and/or co-catalyst, the resulting slurrycan be dewatered to provide a catalyzed particulate, again typically, asa wet cake. The catalyst solution for slurrying the particulate can beprepared from any catalyst source in the present methods, includingfresh or make-up catalyst and recycled catalyst or catalyst solution(infra). Methods for dewatering the slurry to provide a wet cake of thecatalyzed particulate include filtration (gravity or vacuum),centrifugation, and a fluid press.

One particular method suitable for combining coal with a gasificationcatalyst to provide a catalyzed particulate is via ion exchange asdescribed in in previously incorporated U.S. patent application Ser. No.12/178,380 (filed 23 Jul. 2008). Catalyst loading by ion exchangemechanism may be maximized based on adsorption isotherms specificallydeveloped for the coal, as discussed in the incorporated reference. Suchloading provides a catalyzed particulate as a wet cake. Additionalcatalyst retained on the ion-exchanged particulate wet cake, includinginside the pores, can be controlled so that the total catalyst targetvalue can be obtained in a controlled manner. The catalyst loaded anddewatered wet cake may contain, for example, about 50 % moisture. Thetotal amount of catalyst loaded can be controlled by controlling theconcentration of catalyst components in the solution, as well as thecontact time, temperature and method, as can be readily determined bythose of ordinary skill in the relevant art based on the characteristicsof the starting coal.

Alternatively, the slurried particulates may be dried with a fluid bedslurry drier (i.e., treatment with superheated steam to vaporize theliquid), or the solution evaporated, to provide a dry catalyzedparticulate.

The catalyzed particulates may comprise greater than about 10%, greaterthan about 20%, greater than about 30%, greater than about 40%, greaterthan about 50%, greater than about 70%, greater than about 85%, orgreater than about 90% of the total amount of the gasification catalystof the particulate composition. The percentage of total gasificationcatalyst that is associated with the particulates can be determinedaccording to methods known to those skilled in the art.

Separate particulates, with or without catalyst, can be blendedappropriately to control, for example, the total catalyst loading orother qualities of the particulate composition, as discussed previously.The appropriate ratios of the separate particulates will depend on thequalities of the feedstocks as well as the desired properties of theparticulate composition. For example, a biomass char particulate and acatalyzed non-biomass particulate can be combined in such a ratio toyield a particulate composition having a predetermined ash content, asdiscussed previously.

Separate particulates, as one or more dry particulates and/or one ormore wet cakes, can be combined by any methods known to those skilled inthe art including, but not limited to, kneading, and vertical orhorizontal mixers, for example, single or twin screw, ribbon, or drummixers. The resulting particulate composition can be stored for futureuse or transferred to a feed operation for introduction into agasification reactor. The particulate composition can be conveyed tostorage or feed operations according to any methods known to thoseskilled in the art, for example, a screw conveyer or pneumatictransport.

Ultimately, the particulate composition may be dried, under a flow of aninert gas, with a fluid bed slurry drier (i.e., treatment withsuperheated steam to vaporize the liquid), or the solution evaporated,to provide a catalyzed particulate typically having a residual moisturecontent of, for example, less than about 8 wt %, or less than about 6 wt%, or less than about 4 wt %.

In an embodiment of the third aspect, the present invention provides aprocess for preparing a particulate composition according to the firstaspect, the process comprising the steps of: (a) providing a firstparticulate carbonaceous feedstock that is a biomass char, a secondparticulate carbonaceous feedstock that is a biomass, non-biomass, ormixture thereof, and a gasification catalyst; (b) contacting the firstcarbonaceous feedstock and the second carbonaceous feedstock with anaqueous solution comprising at least a portion of the gasificationcatalyst to form a slurry; (c) dewatering the slurry to form acatalyst-loaded wet cake; and (d) thermally treating the wet coal cakeunder a flow of inert dry gas to form the particulate composition.

In another embodiment of the third aspect, the present inventionprovides a process for preparing a particulate composition according tothe first aspect, the process comprising the steps of: (a) providing afirst particulate carbonaceous feedstock that is a biomass char, asecond particulate carbonaceous feedstock that is a biomass,non-biomass, or mixture thereof, and a gasification catalyst; (b)contacting the first carbonaceous feedstock with an aqueous solutioncomprising at least a portion of the gasification catalyst to form aslurry; (c) dewatering the slurry to form a catalyst-loaded wet cake;(d) mixing the catalyst-loaded wet cake with and the second carbonaceousfeedstock to form a mixture; and (e) thermally treating the mixtureunder a flow of inert dry gas to form the particulate composition.

In another embodiment of the third aspect, the present inventionprovides a process for preparing a particulate composition according tothe first aspect, the process comprising the steps of: (a) providing afirst particulate carbonaceous feedstock that is a biomass char, asecond particulate carbonaceous feedstock that is a biomass,non-biomass, or mixture thereof, and a gasification catalyst; (b)contacting the second carbonaceous feedstock with an aqueous solutioncomprising at least a portion of the gasification catalyst to form aslurry; (c) dewatering the slurry to form a catalyst-loaded wet cake;(d) mixing the catalyst-loaded wet cake with and the first carbonaceousfeedstock to form a mixture; and (e) thermally treating the mixtureunder a flow of inert dry gas to form the particulate composition.

Catalytic Gasification Methods

The particulate compositions of the present disclosure are particularlyuseful in integrated gasification processes for converting biomass andnon-biomass to combustible gases, such as methane. The gasificationreactors for such processes are typically operated at moderately highpressures and temperature, requiring introduction of the particulatecomposition to the reaction zone of the gasification reactor whilemaintaining the required temperature, pressure, and flow rate of thefeedstock. Those skilled in the art are familiar with feed systems forproviding feedstocks to high pressure and/or temperature environments,including, star feeders, screw feeders, rotary pistons, andlock-hoppers. It should be understood that the feed system can includetwo or more pressure-balanced elements, such as lock hoppers, whichwould be used alternately.

In some instances, the particulate composition can be prepared atpressures conditions above the operating pressure of gasificationreactor. Hence, the particulate composition can be directly passed intothe gasification reactor without further pressurization.

Any of several catalytic gasifiers can be utilized. Suitablegasification reactors include counter-current fixed bed, co-currentfixed bed, fluidized bed, entrained flow, and moving bed reactors.

The particulate compositions are particularly useful for gasification atmoderate temperatures of at least about 450° C., or of at least about600° C. or above, to about 900° C., or to about 750° C., or to about700° C.; and at pressures of at least about 50 psig, or at least about200 psig, or at least about 400 psig, to about 1000 psig, or to about700 psig, or to about 600 psig.

The gas utilized in the gasification reactor for pressurization andreactions of the particulate composition typically comprises steam, andoptionally, oxygen or air, and are supplied to the reactor according tomethods known to those skilled in the art. For example, any of the steamboilers known to those skilled in the art can supply steam to thereactor. Such boilers can be powered, for example, through the use ofany carbonaceous material such as powdered coal, biomass etc., andincluding but not limited to rejected carbonaceous materials from theparticulate composition preparation operation (e.g., fines, supra).Steam can also be supplied from a second gasification reactor coupled toa combustion turbine where the exhaust from the reactor is thermallyexchanged to a water source and produce steam. Alternatively, the steammay be provided to the gasification reactor as described previouslyincorporated U.S. patent applications Ser. No. ______, entitled “STEAMGENERATION PROCESSES UTILIZING BIOMASS FEEDSTOCKS” (attorney docket no.FN-0020 US NP1), and Ser. No. ______, entitled “REDUCED CARBON FOOTPRINTSTEAM GENERATION PROCESSES” (attorney docket no. FN-0021 US NP1).

Recycled steam from other process operations can also be used forsupplying steam to the reactor. For example, when the slurriedparticulate composition is dried with a fluid bed slurry drier, asdiscussed previously, the steam generated through vaporization can befed to the gasification reactor.

The small amount of required heat input for the catalytic gasificationreaction can be provided by superheating a gas mixture of steam andrecycle gas feeding the gasification reactor by any method known to oneskilled in the art. In one method, compressed recycle gas of CO and H₂can be mixed with steam and the resulting steam/recycle gas mixture canbe further superheated by heat exchange with the gasification reactoreffluent followed by superheating in a recycle gas furnace.

A methane reformer can be included in the process to supplement therecycle carbon monoxide and hydrogen fed to the reactor to ensure thatenough recycle gas is supplied to the reactor so that the net heat ofreaction is as close to neutral as possible (only slightly exothermic orendothermic), in other words, that the reaction is run under thermallyneutral conditions. In such instances, methane can be supplied for thereformer from the methane product, as described below.

Reaction of the particulate composition under the described conditionstypically provides a crude product gas and a char. The char produced inthe gasification reactor during the present processes typically isremoved from the gasification reactor for sampling, purging, and/orcatalyst recovery. Methods for removing char are well known to thoseskilled in the art. One such method taught by EP-A-0102828, for example,can be employed. The char can be periodically withdrawn from thegasification reactor through a lock hopper system, although othermethods are known to those skilled in the art. Processes have beendeveloped to recover alkali metal from the solid purge in order toreduce raw material costs and to minimize environmental impact of acatalytic gasification process.

The char can be quenched with recycle gas and water and directed to acatalyst recycling operation for extraction and reuse of the alkalimetal catalyst. Particularly useful recovery and recycling processes aredescribed in U.S. Pat. No. 4,459,138, as well as previously incorporatedU.S. Pat. No. 4,057,512 and US2007/0277437A1, and previouslyincorporated U.S. patent application Ser. Nos. 12/342,554, 12/342,715,12/342,736 and 12/343,143. Reference can be had to those documents forfurther process details.

Crude product gas effluent leaving the gasification reactor can passthrough a portion of the gasification reactor which serves as adisengagement zone where particles too heavy to be entrained by the gasleaving the gasification reactor (i.e., fines) are returned to thefluidized bed. The disengagement zone can include one or more internalcyclone separators or similar devices for removing fines andparticulates from the gas. The gas effluent passing through thedisengagement zone and leaving the gasification reactor generallycontains CH₄, CO₂, H₂ and CO, H₂S, NH₃, unreacted steam, entrainedfines, and other contaminants such as COS.

The gas stream from which the fines have been removed can then be passedthrough a heat exchanger to cool the gas and the recovered heat can beused to preheat recycle gas and generate high pressure steam. Residualentrained fines can also be removed by any suitable means such asexternal cyclone separators, optionally followed by Venturi scrubbers.The recovered fines can be processed to recover alkali metal catalyst,or directly recycled back to feedstock preparation as described inpreviously incorporated U.S. patent application Ser. No. ______,entitled “CARBONACEOUS FINES RECYCLE” (attorney docket no. FN-0028 USNP1).

The gas stream from which the fines have been removed can be fed to COShydrolysis reactors for COS removal (sour process) and further cooled ina heat exchanger to recover residual heat prior to entering waterscrubbers for ammonia recovery, yielding a scrubbed gas comprising atleast H₂S, CO₂, CO, H₂, and CH₄. Methods for COS hydrolysis are known tothose skilled in the art, for example, see U.S. Pat. No. 4,100,256.

The residual heat from the scrubbed gas can be used to generate lowpressure steam. Scrubber water and sour process condensate can beprocessed to strip and recover H₂S, CO₂ and NH₃; such processes are wellknown to those skilled in the art. NH₃ can typically be recovered as anaqueous solution (e.g., 20 wt %).

A subsequent acid gas removal process can be used to remove H₂S and CO₂from the scrubbed gas stream by a physical absorption method involvingsolvent treatment of the gas to give a cleaned gas stream. Suchprocesses involve contacting the scrubbed gas with a solvent such asmonoethanolamine, diethanolamine, methyldiethanolamine,diisopropylamine, diglycolamine, a solution of sodium salts of aminoacids, methanol, hot potassium carbonate or the like. One method caninvolve the use of Selexol® (UOP LLC, Des Plaines, Ill. USA) orRectisol® (Lurgi A G, Frankfurt am Main, Germany) solvent having twotrains; each train consisting of an H₂S absorber and a CO₂ absorber. Thespent solvent containing H₂S, CO₂ and other contaminants can beregenerated by any method known to those skilled in the art, includingcontacting the spent solvent with steam or other stripping gas to removethe contaminants or by passing the spent solvent through strippercolumns. Recovered acid gases can be sent for sulfur recoveryprocessing. The resulting cleaned gas stream contains mostly CH₄, H₂,and CO and, typically, small amounts of CO₂ and H₂O. Any recovered H₂Sfrom the acid gas removal and sour water stripping can be converted toelemental sulfur by any method known to those skilled in the art,including the Claus process. Sulfur can be recovered as a molten liquid.One method for removing acid gases from the scrubbed gas stream isdescribed in previously incorporated U.S. patent application Ser. No.______, entitled “SELECTIVE REMOVAL AND RECOVERY OF ACID GASES FROMGASIFICATION PRODUCTS” (attorney docket no. FN-0023 US NP1).

The cleaned gas stream can be further processed to separate and recoverCH₄ by any suitable gas separation method known to those skilled in theart including, but not limited to, cryogenic distillation and the use ofmolecular sieves or ceramic membranes. One method for separating andrecovering methane from the cleaned gas stream is described inpreviously incorporated U.S. patent application Ser. No. ______,entitled “PROCESS AND APPARATUS FOR THE SEPARATION OF METHANE FROM A GASSTREAM” (attorney docket no. FN-0022 US NP1).

Typically, two gas streams can be produced by the gas separationprocess, a methane product stream and a syngas stream (H₂ and CO). Thesyngas stream can be compressed and recycled to the gasificationreactor. If necessary, a portion of the methane product can be directedto a reformer, as discussed previously and/or a portion of the methaneproduct can be used as plant fuel.

EXAMPLES Example 1

Feedstock Preparation

Switchgrass can be dried and crushed to produce a particulate having anaverage size of about 250 microns. The biomass feedstock can be providedto a combustion reactor fed by an enriched oxygen source. The resultingexhaust gas from the combustion reactor would contain hot CO₂. Theexhaust gas can be passed through a heat exchanger in contact with awater source to produce steam, a portion of which can be provided to asteam turbine to generate electricity. The biomass char produced fromthe biomass combustion reactor can be withdrawn and directed to afeedstock preparation operation where the biomass char can be crushed toa particle size ranging from about 0.85 to about 1.4 mm. Fines (<0.85mm) can be separated from the crushed biomass char by vibratoryscreening.

Separately, as-received coal (Powder River Basin) can be stage-crushedto maximize the amount of material having particle sizes ranging fromabout 0.85 to about 1.4 mm. Fines (<0.85 mm) can be separated from thecrushed materials by vibratory screening and the crushed coal can beslurried with an aqueous solution of potassium carbonate and dewateredto provided a wet cake of a catalyzed coal feedstock.

The wet cake of the catalyzed coal feedstock can be kneaded together, ina 9:1 w/w ratio on a dry basis, with the crushed biomass char to providea blended feedstock which can be dried via a fluid bed slurry drier to afinal state having about 5 wt % residual moisture.

Example 2

Catalytic Gasification

A portion of the generated steam from the heat exchanger of Example 1can be superheated and then introduced to a fluidized bed gasificationreactor (catalytic gasifier) supplied with the blended feedstock ofExample 1. The blended feedstock can be introduced under a positivepressure of nitrogen. Typical conditions for the catalytic gasifiercould be: total pressure, 500 psi and temperature, 1200° F. The effluentof the catalytic gasifier could contain methane, CO₂, H₂, CO, water,H₂S, ammonia, and nitrogen, which can be passed to a scrubber to removeammonia and an acid gas removal unit to remove H₂S and CO₂. The CO₂ canbe recovered.

1. A particulate composition having a particle distribution sizesuitable for gasification in a fluidized bed zone, the particulatecomposition comprising an intimate mixture of: (a) a first carbonaceousfeedstock that is a biomass char; (b) a second carbonaceous feedstockthat is a biomass, non-biomass, or a mixture thereof, and (c) agasification catalyst which, in the presence of steam and under suitabletemperature and pressure, exhibits gasification activity whereby aplurality of gases including methane and at least one or more ofhydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia andother higher hydrocarbons are formed, wherein: (i) the firstcarbonaceous feedstock and second carbonaceous feedstock are present inthe particulate composition at a weight ratio of from about 5:95 toabout 95:5; and (ii) the gasification catalyst comprises a source of atleast one alkali metal and is present in an amount sufficient toprovide, in the particulate composition, a ratio of alkali metal atomsof the gasification catalyst to carbon atoms ranging from about 0.01 toabout 0.10, wherein the biomass char comprises at least a portion of thesource of at least one alkali metal.
 2. The particulate compositionaccording to claim 1, wherein a portion of the gasification catalyst isloaded on at least one of the first carbonaceous feedstock and thesecond carbonaceous feedstock.
 3. The particulate composition accordingto claim 1, wherein the alkali metal comprises potassium, sodium orboth.
 4. The particulate composition according to claim 1, wherein thealkali metal is potassium.
 5. The particulate composition according toclaim 1, wherein the biomass char comprises all of the gasificationcatalyst.
 6. The particulate composition according to claim 5, whereinthe alkali metal is potassium.
 7. The particulate composition accordingto claim 1, having a particle size ranging from about 25 microns toabout 2500 microns.
 8. The particulate composition according to claim 1,having a residual moisture content of less than about 4 wt. %.
 9. Theparticulate compositions according to the claim 1, wherein the secondcarbonaceous feedstock is a non-biomass.
 10. A process for converting aparticulate composition into a plurality of gaseous products, theprocess comprising the steps of: (a) supplying a particulate compositionaccording to claim 1 to a gasifying reactor; (b) reacting theparticulate composition in the gasifying reactor in the presence ofsteam and under suitable temperature and pressure to form a plurality ofgaseous including methane and at least one or more of hydrogen, carbonmonoxide, carbon dioxide, hydrogen sulfide, ammonia and other higherhydrocarbons; and (c) at least partially separating the plurality ofgaseous products to produce a stream comprising a predominant amount ofone of the gaseous products.
 11. The process according to claim 10,wherein the stream comprises a predominant amount of methane.
 12. Theprocess according to claim 10, wherein a char is formed in step (b), andthe char is removed from the gasifying reactor and sent to a catalystrecovery and recycle process.
 13. The process according to claim 12,wherein the gasification catalyst comprises gasification catalystrecycled from the catalyst recovery and recycle process.
 14. A processfor preparing a particulate composition, the process comprising thesteps of: (a) providing a first particulate carbonaceous feedstock thatis a biomass char, a second particulate carbonaceous feedstock that is abiomass, non-biomass, or mixture thereof, and, optionally, an alkalimetal gasification catalyst which, in the presence of steam and undersuitable temperature and pressure, exhibits gasification activitywhereby a plurality of gases including methane and at least one or moreof hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, ammoniaand other higher hydrocarbons are formed from the particulatecomposition; (b) mixing the first particulate carbonaceous feedstock,the second particulate carbonaceous feedstock and, optionally, thealkali metal gasification catalyst to form a mixture; and (c) optionallythermally treating the mixture under a flow of inert dry gas to form theparticulate composition, wherein the gasification catalyst comprises asource of at least one alkali metal and is present in an amountsufficient to provide, in the particulate composition, a ratio of alkalimetal atoms of the gasification catalyst to carbon atoms ranging fromabout 0.01 to about 0.10, wherein the biomass char comprises at least aportion of the source of at least one alkali metal.
 15. The processaccording to claim 14, wherein the first carbonaceous feedstock andsecond carbonaceous feedstock are contacted separately with an aqueoussolution comprising at least a portion of the gasification catalyst toform first and second slurries; the first and second slurries aredewatered separately to form first and second catalyst-loaded wet cakes;and the first and second catalyst-loaded wet cakes are mixed to form themixture.
 16. The process according to claim 14, wherein the firstcarbonaceous feedstock and second carbonaceous feedstock are contactedseparately with an aqueous solution comprising at least a portion of thegasification catalyst to form first and second slurries; the first andsecond slurries are dewatered separately to form first and secondcatalyst-loaded wet cakes; the first and second catalyst-loaded wetcakes are separately thermally treated to form first and second dryparticulates; and the first and second dry particulates are mixed toform the mixture.
 17. The process according to claim 14, wherein thefirst carbonaceous feedstock and second carbonaceous feedstock are mixedto form a blend; the blend is contacted with an aqueous solutioncomprising at least a portion of the gasification catalyst to form aslurry; and the slurry is dewatered to form a catalyst-loaded wet cakewhich is the mixture.
 18. The process according to claim 14, wherein thefirst carbonaceous feedstock is contacted with an aqueous solutioncomprising at least a portion of the gasification catalyst to form aslurry; the slurry is dewatered to form a catalyst-loaded wet cake; andthe catalyst-loaded wet-cake is mixed with the second carbonaceousfeedstock to form the mixture.
 19. The process according to claim 14,wherein the second carbonaceous feedstock is contacted with an aqueoussolution comprising at least a portion of the gasification catalyst toform a slurry; the slurry is dewatered to form a catalyst-loaded wetcake; and the catalyst-loaded wet-cake is mixed with the firstcarbonaceous feedstock to form the mixture.
 20. The process according toclaim 14, wherein the first carbonaceous feedstock and the secondcarbonaceous feedstocks are mixed to form the mixture.